Continuous Flow Analysis (CFA) is the umbrella term for automated analytical methods in which sample and reagents are brought together and mixed while flowing continuously through tubing, reaction coils, and a detector. Unlike discrete or batch methods, where individual sample portions are pipetted into vessels and measured statically, CFA systems process a continuous stream, enabling high throughput with minimal manual intervention.
The two principal CFA techniques are Segmented Flow Analysis (SFA), where regular air bubbles divide the stream into discrete reacting segments, and Flow Injection Analysis (FIA), where a precise sample plug is injected into a flowing reagent stream without air segmentation. Both achieve the same fundamental goal — bringing sample and reagents together under controlled, reproducible conditions — but differ in how they manage mixing and carryover.
CFA instruments share a common basic architecture: a peristaltic pump, manifold (where sample and reagents combine), reaction coil (where the chemistry develops), and detector (typically photometric, amperometric, or fluorometric). The specific chemistry for each analyte is contained in a method cartridge or defined by the manifold tubing configuration.
For analytical laboratories in mining, environmental consulting, and water utilities, CFA is an attractive choice because validated methods exist for a wide range of priority analytes — cyanide fractions, nutrient species (ammonia, nitrate, nitrite, phosphorus, silica), metals, and many others — in a single instrument format. A laboratory can change analytes by swapping chemistry cartridges rather than purchasing separate instruments for each parameter.
The FS3700 Chemistry Analyser from OI Analytical represents the current generation of multi-method CFA instrumentation. It supports SFA, FIA, iSFA, and SFIA on the same platform, with throughputs from 20 to 90 analyses per hour per channel depending on method.
Key Points
- Umbrella term for SFA and FIA
- Sample and reagents flow continuously through tubing and detector
- Higher throughput and better reproducibility than manual batch methods
- Validated methods available for cyanide, nutrients, metals, and other parameters
- Modular chemistry allows the same instrument to run multiple analytes
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Frequently Asked Questions
What is the advantage of continuous flow analysis over manual batch methods?
CFA systems can run 20 to 90 or more samples per hour per channel with minimal operator involvement, compared to perhaps 10 to 20 per hour for a skilled analyst doing manual colorimetry. CFA also reduces operator-to-operator variability because the chemistry is fully automated, and carryover between samples is controlled by the instrument rather than by manual washout.
Can one CFA instrument run multiple analytes simultaneously?
Yes, in multi-channel configurations. Each channel has its own pump lines and chemistry, so the same sample stream can be split and sent to two or more channels for simultaneous measurement of different analytes. The FS3700, for example, can run WAD cyanide on one channel while measuring ammonia or nitrate on another.